ABSTRACT Steady-state natural convection in open enclosures has been widely studied; however, transient natural convection and influence of obstacle position in such configurations remain insufficiently explored, particularly through interferometric study. The present study addresses this gap by performing real-time transient experiments using Mach-Zehnder interferometry in a partially open square enclosure containing an adiabatic cylindrical obstacle and a heat source at bottom wall. The enclosure has a partial opening occupying 50% of the left vertical wall height. The effects of obstacle position and Rayleigh number 2.35 × 10 7 ≤ Ra ≤ 1.34 × 10 8 on transient and steady natural convection behavior are systematically investigated. Experimental temperature fields obtained from interferograms are compared with numerical predictions using a 2D laminar model in ANSYS Fluent. The results show that thermal plume development intensifies with time and exhibits faster, more irregular evolution at higher Rayleigh numbers. Heat transfer is strongly influenced by obstacle position, with maximum and minimum average Nusselt numbers observed when the obstacle is located at the bottom and left positions, respectively. A steady-state enhancement of up to 16% in average Nusselt number is achieved by relocating the obstacle from the left to the bottom position. Obstacle placement significantly affects flow structure, maximum cavity temperature, and exit velocity at the opening.

Sustainable dropwise condensation technology is crucial for applications in high-performance thermal management, energy conversion, and desalination. However, conventional condensation surfaces often suffer from low droplet departure efficiency and gravity dependence, limiting their practical application in advanced heat exchangers. Here, we report a dual-layer composite surface, composed of a slippery Janus copper mesh and a wedge-shaped microgrooved substrate (SJM-WM), which enables gravity-independent droplet departure via interfacial transport. This design spatially decouples vapor condensation on the upper Janus mesh and droplet transport in the lower substrate, leveraging synergistic wettability gradients and Laplace pressure-driven directional flow. By tailoring mesh pore size, the Laplace pressure and droplet coalescence dynamics are effectively regulated, achieving a small droplet departure diameter of 98 ± 2 μm, which is comparable to the bouncing-off behavior on superhydrophobic surfaces. The SJM-WM surface enhances condensation heat transfer by 23.1% and 102.4% compared to state-of-the-art hydrophobic-superhydrophilic wedge-grooved surfaces (HB-SHL) and hydrophobic copper mesh-wedged microgroove composite surfaces (HBM-WM), respectively. This work provides a promising strategy for advancing high-performance thermal management systems in power-dense electronics.

Abstract Thermal interface materials serve as critical components for facilitating heat transfer between cells and the cooling system in electric vehicle battery packs. However, internal porosity introduced during manufacturing can substantially reduce their thermal conductivity. In this study, the internal pore structure of actual thermal interface material samples was characterised using X-ray computed tomography, and porosity was quantitatively determined through a regression-based thresholding method implemented in MATLAB. The resulting pore distributions were incorporated into finite volume-based thermal simulations in Ansys Fluent, enabling the calculation of effective thermal conductivity as a function of porosity ratio. The simulated effective thermal conductivity values closely matched those predicted by the effective medium theory, particularly at low porosity levels. In contrast, conjugate thermal-fluid analyses of electric vehicle battery packs revealed that local temperature increases of up to 1.3°C can occur depending on pore location and distribution. These findings indicate that effective medium theory-based average conductivity models are inadequate for capturing localized thermal hotspots. Consequently, thermal interface material application processes and design strategies should address not only the allowable porosity threshold but also the spatial distribution of pores to ensure robust thermal management in electric vehicle battery systems.

Effects of heat transfer medium with carbon nano tube and nano silicon carbide coatings on thermal characteristics of half cylindrical shaped solar greenhouse dryer

Due to the demand of unmanned helicopters for drag reduction and rain-proof, the helicopter nacelle must be sealed. It will lead to a decrease in the heat transfer efficiency of the radiator, and the output power of the engine will drop dramatically. The helicopter's flight safety will be seriously jeopardized, especially when the helicopter is hovering (maximum engine power is needed). Currently, active cooling by equipping the radiator with a fan is the only solution, and the heat transfer efficiency of the radiator could be controlled by fan. Therefore, the performance of the fan directly affects the flight safety of the whole system. In this study, the Airfoils 30, suitable for low Reynolds number flows, is adopted to design the fan blade considering the characteristics of helicopter heat sink miniaturization and high integration. Then, a three-dimensional CFD (computational fluid dynamics) k-omega SST model is developed to investigate the effects of fan blade torsion angle, chord length, mounting angle and the number of blades on the performance of the fan. Furthermore, the constraints of radiator dimension, air flow resistance on the performance of the fan are considered comprehensively to finalize the new fan configuration. The optimised parameters of fan suitable for high flow rate (above 1.17kg/s) are chord length is55mm, torsion angle is 26°, mounting angle is 39° and the blade number is 7. The fan efficiency increases about 13.6%. The power consumption decreases about 9.5% (about 73 W). The fan rotational speed decreases 10.5%. The improvement of fan efficiency is a key measure for energy conservation and carbon reduction in unmanned helicopter systems. The 73 W power consumption of the fan decrease indicates that 1.2kg green-house gas emission reduces per day. The lower power consumption will result in a 0.14% cruising endurance increase. The fan is then manufactured by additive manufacturing based on CFD optimization results. This deep integration between CFD and additive manufacturing reduces trial and error costs and energy consumption. It also shows the promising future of UAV components autonomous manufacturing. Finally, the experiment is conducted in lab under 40℃. The experimental results indicate that the maximum output power of the engine is over than 90kW. Based on the helicopter main rotor performance curve, the helicopter could hover indefinitely with 500kg loading under 40°C. It is a criterion to identify the designing success.

Abstract - Heat exchangers play a crucial role in various industries, including power generation, chemical processing especially ventilation and air conditioning. Performance and efficiency of heat exchangers is observed to have dependent on various fluid flow parameters like Nusselt and Reynold numbers. In this research work, an attempt is made to investigate the performance of dimpled tube heat exchangers under different flow conditions, characterized by the Reynolds number and Nusselt Number. Results show that dimpled tubes outperform smooth tubes, with significant improvements in heat transfer rates and moderate increases in pressure drop. From tabular values and plots it was found that using spherical dimples leads to a significant increase in the heat transfer rate as compared to that of a normal tube without dimples. Also, it was seen that the change of dimple arrangement from inline to staggered arrangement enhances the heat transfer characteristics to a noticeable amount as compared to others but may further be studied for higher scale implementation with some corresponding moderations. This research has important implications for industries that rely on heat exchangers, offering a potential solution to improve their efficiency and reduce energy consumption which can aid in developing more efficient and sustainable heat transfer systems. Key Words: heat transfer coefficient (h), dimpled tube, nusselt Number (Nu), reynolds Number (Re), smooth tubes

During on-site welding operations, the sealant coated on anchor bolt surfaces can be ignited by hot particles or localized sparks, potentially triggering a fire hazard. This combustion process involves a complex multi-physics coupling among sealant combustion, convective and radiative heat transfer, and three-dimensional heat conduction in solids. To resolve this coupling, a simulation strategy is proposed that correspondingly integrates the Fire Dynamics Simulator (FDS, version 6.7.6) for modeling combustion and radiation with ABAQUS (2024) for simulating conductive heat transfer in solids. The proposed method is validated against experimental measurements, showing close agreement in temperature evolution. It also demonstrates robustness across varying geometric scales, thereby confirming its reliability for predicting thermal response. Using this validated method, simulations are performed to analyze the fire behavior of an anchor rod-sealant system. Results show that the burning sealant can raise anchor rod temperatures above 900 °C and lead to rapid flame spread between adjacent rods. Furthermore, a sensitivity analysis of thermophysical parameters identifies critical thresholds for fire safety optimization: sealants with an ignition temperature > 280 °C and thermal conductivity ≥ 0.26 W/(m·K) demonstrate effective self-extinguishing properties, while specific heat capacity can retard flame growth. These findings provide a robust numerical framework and quantitative guidelines for the fire-safe design of bridge anchorage systems.

Abstract Accurate prediction of H2-blended combustion requires advanced radiation modeling, as the radiation model plays a critical role in the turbulence-chemistry-radiation coupling inherent to such flames. To address the issue of accurately predicting the gas and soot thermal radiation characteristics in natural gas combustion blended with a high ratio of hydrogen, an improved global thermal radiation model based on weighed-sum-of-gray-gases (WSGG) principle was proposed. The proposed model containing H2O and CO2 was developed based on a line-by-line (LBL) method using the HITEMP 2010 database. The coefficients were applicable to a total pressure range of 1 ∼ 10 atm, a temperature range of 400 ∼ 2500 K, a H2O/CO2 molar ratio range of 2.25 ∼ 5, and a partial pressure path length range of 0.001 ∼ 60 atm·m, verified using benchmark emissivity and a series of one- and two-dimensional heat transfer cases. The proposed WSGG model was then applied to numerical simulation of a 40-kW combustion furnace. The results were compared with those obtained using default model of Fluent software, and the influence of soot radiation inclusion was discussed, indicating that pressurization and the presence of soot enhance radiative heat transfer, and the improved global model can perform more accurate medium radiation calculations compared to the previous model developed for conventional fuels, which provide a basis for furnace design of hydrogen-blended natural gas combustion.

High regeneration energy demand remains a critical barrier to the large-scale deployment of ethanolamine-based (MEA-based) CO2 capture. This study adopts an Al2O3 ceramic-membrane heat exchanger (CMHE) to recover both sensible and latent heat from the stripped gas. Experiments confirm that heat and mass transfer within the CMHE follow a coupled mechanism in which capillary condensation governs trans-membrane water transport, while heat conduction through the ceramic membrane dominates heat transfer, which accounts for more than 80%. Guided by this mechanism, systematic structural optimization was conducted. Alumina was identified as the optimal heat exchanger material due to its combined porosity, thermal conductivity, and corrosion resistance. Among the tested pore sizes, CMHE-4 produces the strongest capillary-condensation enhancement, yielding a heat recovery flux (q value) of up to 38.8 MJ/(m2 h), which is 4.3% and 304% higher than those of the stainless steel heat exchanger and plastic heat exchanger, respectively. In addition, Length-dependent analyses reveal an inherent trade-off: shorter modules achieved higher q (e.g., 14–42% greater for 200-mm vs. 300-mm CMHE-4), whereas longer modules provide greater total recovered heat (Q). Scale-up experiments demonstrated pronounced non-linear performance amplification, with a 4 times area increase boosting q by only 1.26 times under constant pressure. The techno-economic assessment indicates a simple payback period of ~2.5 months and a significant reduction in net capture cost. Overall, this work establishes key design parameters, validates the governing transport mechanism, and provides a practical, economically grounded framework for implementing high-efficiency CMHEs in MEA-based CO2 capture.

This work analyzes a shape memory alloy Stirling heat engine through an integrated thermal, mechanical, and materials approach. It builds on our previously published framework by generalizing behavior of shape memory alloys (SMA) beyond the nanoscale and extends it to elastocaloric applications, where mechanical work can be used to induce the stress-induced phase transformation. Parallels between stress-strain and enthalpy-temperature behavior underline this extension. Heat engine performance is evaluated in terms of torque and speed, and consideration is given to fatigue service life. Heat transfer and transformation energetics are examined with implications for heat engine performance. The resulting work supports shape memory alloy based heat engines and refrigerators for thermal management in space applications.

Abstract This paper introduces a quantum-enhanced finite element method (FEM) designed for noisy intermediate-scale quantum (NISQ) devices, leveraging variational quantum algorithms (VQAs) to solve engineering partial differential equations (PDEs). We demonstrate the framework by solving the Euler-Bernoulli beam and the NAFEMS T4 heat transfer problems, which involve Dirichlet, Neumann, and Robin boundary conditions. A key innovation is a ``set-to-zero" strategy that incorporates boundary conditions through a correction matrix, $K_{bc}$, allowing for flexible imposition at any node without domain decomposition. The global stiffness matrix is decomposed into a constant number of Pauli terms, $O(1)$, using the method by Sato et al., while boundary terms are handled with a sublinearly scaling Partial Pauli Measurement (PPM) technique. The algorithm achieves logarithmic qubit scaling ($n = \lceil \log_2 N \rceil $ qubits for N degrees of freedom) and employs shallow, hardware-efficient circuits with empirically trainable depth for small-scale systems. Validation on the Qiskit statevector simulator shows high accuracy. For the Euler-Bernoulli beam problem with 4 to 64 degrees of freedom, the algorithm achieves relative errors of 0.5–1.5\% and fidelities of 0.998–0.999. For the NAFEMS T4 heat transfer benchmark, a 5.4\% relative error is observed. The VQA converges robustly within 77–350 iterations, though barren plateaus are a known challenge for scaling to larger systems. This work establishes a scalable framework for quantum FEM, offering a significant memory advantage over classical methods and advancing the potential for quantum-enhanced engineering simulations.

This work presents a straightforward procedure for constructing the solution to the steady-state energy-transfer process in a system of two convex, opaque, gray bodies, with the aim of determining the temperature distribution within these bodies when separated by a vacuum. The methodology proposed in this work combines a sequence of elements that are functions obtained from the solution of uncomplicated, well-known linear, uncoupled heat transfer problems, thereby enabling solutions to be obtained using tools found in basic engineering textbooks. Specifically, these well-known problems resemble classical conduction-convection heat transfer problems, in which the boundary condition is described by the noteworthy Newton’s law of cooling. The limit of sequences of elements that are solutions to straightforward linear problems corresponds to the original, complex, coupled nonlinear problem. The convergence of these sequences is mathematically proven. The phenomenon (considered in this work) encompasses those involving black bodies. Since each element of the sequence arises from a well-known linear problem, numerical approximations can be used to obtain it, yielding a simple and powerful tool for simulations. Some presented results highlight the importance of considering thermal interaction between the two bodies, even in the absence of physical contact. In particular, the alterations in the temperature distributions of two separate gray bodies are explicitly shown to result from their thermal interaction.

Abstract Localized heat sources within wheat piles in underground storage can induce condensation and mold formation, thereby severely compromising grain storage safety. Investigating the influence of localized heating on the internal temperature evolution is crucial for ensuring safe grain preservation. This study developed a coupled heat and mass transfer numerical model that conceptualizes the wheat pile as a solid skeleton with interstitial air domains to analyze the temperature evolution in underground storage. Through 16 cases with varying quantities and surface temperatures of plane heat sources in condensation-prone areas, the impacts on temperature distribution were examined, and the effectiveness of natural ventilation in mitigating thermal inhomogeneity was evaluated. The results revealed that during static storage in winter, a localized heating zone gradually forms in the upper-middle grain layers with distinct temperature variations across different layers. Secondary heat sources tend to develop above primary heating zone. The natural ventilation shows a certain effectiveness in reducing the temperature of the wheat pile, but the overall cooling effect remains limited. Incorporating heat source temperatures and thermal convection effects into the design of ventilation and thermal management system enables more efficient temperature regulation. This research provides theoretical support for optimizing thermal control strategies in underground grain storage.

Heat exchangers are central to energy and process industries, yet performance is bounded by the trade-off between higher heat transfer and greater pressure drop. This review targets indirect-type heat exchangers and organizes bioinspired strategies through a multi-scale lens of surface, texture, and network scales. It provides a structured comparison of their thermo-hydraulic behaviors and evaluation methods. At the surface scale, control of wettability and liquid-infused interfaces suppresses icing and fouling and stabilizes condensation. At the texture scale, microstructures inspired by shark skin and fish scales regulate near-wall vortices to balance drag reduction with heat-transfer enhancement. At the network scale, branched and bicontinuous pathways inspired by leaf veins, lung architectures, and triply periodic minimal surfaces promote uniform distribution and mixing, improving overall performance. The survey highlights practical needs for manufacturing readiness, durability, scale-up, and validation across operating ranges. By emphasizing analysis across scales rather than reliance on a single metric, the review distills design principles and selection guidelines for next-generation bioinspired heat exchangers.

Coupled heat and moisture transfer in elliptical semi-permeable membrane fiber bundles for membrane distillation desalination.

This paper summarizes achievements in the development of advanced technology utilizing RELAP5-3D for both real-time training simulators and highly detailed simulation-assisted engineering models for different reactor types, including small modular and liquid metal–cooled reactors. Code improvements were made to address major challenges in real-time nuclear power plant simulators to enable high performance, stability, and accuracy concurrently. The code changes, which were accumulated over 3 decades of code applications, include implementation of a smooth transition between different heat transfer and flow regime conditions, Dalton-Gibbs mixture equation solver corrections, and numerical scheme improvements to avoid code aborts and unphysical spikes when transitioning from one-phase to two-phase flow conditions and vice versa. To support training simulator functions, dynamic change of fouling factors, form loss coefficients, and material heat capacity values were implemented. The model development studio is supported by the functionality of interactive changes to Time-Dependent component parameters and constant-type control variable values. The graphical editor gas been added to the framework with rich visualization capabilities, multidimensional components, a XML-based user input deck editor with thermodynamic value validation, and version control functionality. The performance improvements were achieved by means of parallelization techniques when a neutronics code (typically NESTLE) and separate hydraulic systems are running on different computer processors, with the results exchanging functionality support every time advancement step. Engineering simulators are supported by the addition of turbulent mixing code capability in the lateral direction between adjacent reactor core channels. The limitation of a three-digit component number gas been relaxed to enable greater flexibility in deck composition. Supporting software functionality has been added to the 3KEYMASTERTM platform for multidimensional flow simulations and user input deck generation, which uses the outstanding utility of cross-sectional area calculations between the reactor plenum’s cylindrical planar noding and the reactor core cartesian structure utilizing the Greiner-Hormann algorithm. Proposed further code enhancements for multidimensional simulations include the addition of an uneven mesh feature for the cylindrical coordinate system in the planar direction and enabling seamless integration of multidimensional heat structures with hydrodynamic components.

Thermal error is an important obstacle to improve the thermal stability and accuracy of machine tools. A theoretical model of heat transfer and conduction for the high-speed electric spindle of CNC machine tools was established by simplifying the electric spindle into a one-dimensional rod for heat transfer, proving the hysteresis thermal characteristics of the electric spindle. To solve difficulty in predicting machine tool spindles under variable operating conditions. A fuzzy C-means clustering (FCM) algorithm and uncertainty coefficient method (UCM) were proposed to determine temperature sensitive points, and the influence of rotational speed on thermal error was considered to establish a nonlinear autoregressive (NAR) long short-term memory (LSTM) neural network model. The use of Sparrow search algorithm (SSA) for automatic optimization of hyperparameters in the NAR-LSTM model improves the prediction accuracy and modeling efficiency of modeling. Experiments results shows thermal error of the spindle is arisen from 0 to 65 μ m under complex machining conditions, the comprehensive predictive residual of the SSA-NAR-LSTM, LSTM and BP models under variable conditions remained 3, 6.8 and 8 μ m . The predictive accuracy of the SSA-NAR-LSTM model increased over 50% compared to BP and LSTM models. The proposed SSA-NAR-LSTM modeling method is a high-precision and effective method for predicting thermal errors in high-speed electric spindles.

Electrokinetic transport of a Jeffrey microbial trihybrid nano-blood suspension in a ciliated arterial lumen with slip and reaction effects.

Hierarchical MoS2/CuS photonic nanostructure accelerating photothermoelectric conversion of bacterial cellulose based phase change materials.

In this study, the effects of nonlinear thermal radiation, Arrhenius activation energy, and chemical reactions on the flow and heat transfer of a water-based hybrid nanofluid containing SWCNT- [Formula: see text] & MWCNT- [Formula: see text] nanoparticles over a rotating disk are examined. The investigation highlights the combined influence of nonlinear radiation and nanoparticle shape factors on the transport properties of the hybrid fluid. Given that the thermal and structural performance of nanomaterials is strongly dependent on their morphology, special attention is devoted to assessing the role of particle shape variations. The objective of this work is to advance the fundamental understanding of how nonlinear radiative processes, activation energy, and nanoparticle geometry interact in rotating disk flows, thereby contributing to the development of efficient nanofluid based thermal management systems. These materials find applications in energy storage, thermal stability, transistors, and electromagnetic shielding. Given the growing demand for nanotechnology, understanding these effects is crucial for enhancing performance in engineering and energy systems. The governing PDEs are simplified into dimensionless ODEs using similarity transformations. The Successive Over-Relaxation method, executed through a custom MATLAB code, is used to obtain the solutions of these equations. The effects of different parameter values on radial and transversal velocity, as well as heat and mass transfer, are examined using graphical analysis. In addition, tabular data are presented to evaluate the behavior of skin friction, Nusselt number, and Sherwood number under various parametric conditions. The results reveal that velocity diminishes with increasing magnetic parameter values, whereas nonlinear radiation enhances heat transfer. Activation energy augments both concentration and mass transfer, although the latter is influenced by the Schmidt number and the chemical reaction rate. Conversely, temperature decreases with a rise in the Prandtl number. Radial skin friction decreases by about 44% as the magnetic parameter increases, while tangential skin friction magnitude rises by nearly 78% at low suction and around 37% at high suction. Furthermore, the heat transfer rate improves from 25.27% at Rd = 0.5 to 37.18% at Rd = 1.4, indicating an overall enhancement of 11.91%. These outcomes hold practical significance for optimizing fluid behavior and heat transfer in rotating systems, with potential applications in energy systems, heat exchangers, and advanced cooling technologies.